Travel planning systems are used to produce itineraries and prices by selecting suitable travel units from databases containing geographic, scheduling and pricing information. In the airline industry, fundamental travel units include “flights” (sequences of regularly scheduled takeoffs and landings assigned a common identifier) and “fares” (prices published by airlines for travel between two points). The term “itinerary” corresponds to a sequence of flights on particular dates and the term “pricing solution” corresponds to a combination of fares and itineraries that satisfies a travel request and which can be used to provide a ticket for transportation. Travel planning systems such as those offered by various web-sites and computer reservation systems enables individual consumers and travel agents, alike, to search for available faring solutions satisfying a travel query. One such system is the “QPX” travel planning system by ITA Software®. Aspects of the QPX travel planning system are described in U.S. Pat. No. 6,275,808 and assigned to the assignee of the present application and incorporated herein by reference. The faring solutions that are returned to the user (i.e., an individual consumer or travel agent) include all of the information required to book and ticket the itinerary directly in a carrier's inventory system or in a computer reservation system (CRS). For booking a trip, QPX enables users to retrieve a wide range of prices and itineraries of available tickets.